Question

Calculate pH of solution when 50 ml 0.2 N HCl is mixed with 50 ml 0.4 N NaOH:

• A. 1
• B. 2
• C. 10
• D. 13

Answer 1

The correct option is D 13

No. of $\left[H^{+}\right]$ moles $=50\times 0.2=10$ $m$ $mol$

No. of $\left[O{H}^{-}\right]$ moles $=50\times 0.4=20$ $m$ $mol$

$10$ $m$ $mol$ of $O{H}^{-}$ will be left in $100$ $mL$ of water.

$\left[O{H}^{-}\right]=\frac{10\times {10}^{-3}}{100\times {10}^{-3}}={10}^{-1}$

$pOH=1$ and $pH=13$